The present invention is useful with an electromagnetic solenoid valve operable for fluid contol in conjunction with a diaphragm operable valve. Such solenoid valves are known and used to control either hydraulic or pneumatic flow. Such valve combinations are often complex assemblies that are spring biased, operable in conjunction with connecting rods or ball valves, or have flexible diaphragms fabricated of special material. These devices are responsive to variations in current and/or voltage through the solenoid to permit flow through the valve as a function of fluid flow or pressure. Some of these valves operate in a steady state condition (i.e., a direct current flow at a given voltage) where the forces, such as mechanical spring bias, electromagnetic field, and/or fluid pressure, are balanced or calibrated to permit valve operation in a given mode. These valves are not generally electrically adjustable. However, in at least one case there is an adjustable means, such as a screw, to vary the fluid flow and pressure operable against a bias spring to thereby effect a change in the operation of the valve. The bias springs of these various devices are changeable, as are the number of turns of the solenoid coil, the materials of construction, and the sizes of the assemblies. These devices are somewhat complex and relatively expensive to assemble.
Such solenoid valves find particular application in modern automobiles equipped with various microprocessors that receive input signals indicating physical parameters such as exhaust gas oxygen content, vehicle speed, engine RPM, engine temperature, and so forth. Such microprocessors receive these input data signals, and evaluate and/or compare the data to produce a signal which may control fuel input, spark advance or other operating parameters. In the present case such a microprocessor is capable of producing an output signal that will actuate the solenoid valve at a given current amplitude to provide a predictable or desired output from a variable fluid source, such as a manifold vacuum. The microprocessor in the automobile case above can control the duty cycle or on-time of a square wave signal to maintain the fluid pressure or vacuum output at a desired level for a given amperage signal. This control can be achieved even though the engine compartment and solenoid temperatures vary. The current level signal can also be derived from simpler arrangements, such as a signal generator or a simple power supply, when closed loop control is not required.
Thus the present invention is directed to a less complex valve assembly, and in particular to an assembly which is electromagnetically adjustable and operable in response to a varing input electrical signal.